Delivery vehicle for material handling system

ABSTRACT

A method and apparatus are provided for sorting items to a plurality of sort destinations. The items are fed into the apparatus at an input station having a scanning station. The scanning station evaluates one or more characteristics of each item. The items are then loaded onto one of a plurality of independently controlled delivery vehicles. The delivery vehicles are individually driven to sort destinations. Once at the appropriate sort destination, the delivery vehicle ejects the item to the sort destination and returns to receive another item to be delivered. A re-induction conveyor may be provided for receiving select items from the vehicles and conveying the items back to the input station for re-processing. Additionally, a controller is provided to control the movement of the vehicles based on a characteristic each item being delivered by each vehicle. The system may also include vehicles having an assembly for detecting items being loaded onto or discharged from the vehicles.

PRIORITY CLAIM

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/586,247 filed May 3, 2017, which is a continuation ofInternational Patent Application No. PCT/US17/13077 filed Jan. 11, 2017,which claims priority to U.S. Provisional Patent Application No.62/277,253, filed Jan. 11, 2016, U.S. Provisional Patent Application No.62/331,020, filed May 3, 2016 and U.S. Provisional Patent ApplicationNo. 62/374,218, filed Aug. 12, 2016. The entire disclosure of each ofthe foregoing applications is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a material handling system and inparticular to a system operable to receive and sort items using aplurality of automated vehicles.

BACKGROUND OF THE INVENTION

Sorting and retrieving items to fill a customer order can be a laboriousand time consuming. Similarly, may large organizations have extensivestorage areas in which numerous items are stored. Sorting and retrievingitems from the hundreds or thousands of storage areas requiressignificant labor to perform manually. In many fields, automated pickinghas developed to reduce labor cost and improve customer service byreducing the time it takes to fill a customer order. However, the knownsystems of automatically handling the materials are either veryexpensive or have limitations that hamper their effectiveness.Accordingly, there is a need in a variety of material handlingapplications for automatically storing and/or retrieving items.

Additionally, in conveyor or sorter systems, objects are generallytransferred to or from a conveyor and/or from one conveyor to another(e.g., from a feed conveyor to a receiving conveyor). In many automatedmaterial handling systems, such transfers take place only after theobject has reached a specific location (e.g., an object storage and/orretrieval location) along the conveying path. The capacity of a materialhandling system is determined, among other things, by the rate at whicheach object is transferred to and/or from the applicable location.

In some material handling systems, a conveyor may form part of a movablevehicle used to transport objects to, or retrieve the objects from, thelocation where a transfer operation is performed. In material systems ofthis type, failure to rapidly and accurately determine that an objecthas been transferred from or to the conveyor may delay (or prevent) thevehicle from advancing to the next location.

SUMMARY OF THE INVENTION

The Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

The invention provides a number of aspects that may form part of amaterial handling system. The system may include one or more of a numberof aspects of the invention as further described below.

According to one aspect, the invention may provide an apparatus forsorting a plurality of items is provided. The apparatus includes aplurality of sort destinations and a plurality of a plurality ofdelivery vehicles for delivering items to the sort destinations. Acontroller is provided for providing signals for controlling operationof the vehicles. A database for storing a plurality of vehicle movementprofiles is also provided. In response to a characteristic determinedfor an item, the central controller retrieves a vehicle movement profileand the central controller controls the movement of the vehicle inresponse to the retrieved vehicle movement profile. The vehicle movementprofile may comprise one or more of the following: acceleration,deceleration and cornering speed.

According to another aspect, the invention may comprise a track systemfor guiding the delivery vehicles to the sort destinations.

According to another aspect, the invention may comprise a scanner forscanning an item to detect a characteristic of each item, wherein thedetected characteristic is the characteristic determined for an itemthat the controller uses to retrieve a vehicle movement profile. Thedetected characteristic may be a product identification code for theitem.

According to yet another aspect, the detected characteristic may be oneof the length, width, height, weight or shape of the item.

According to another aspect, the invention provides an apparatus forsorting a plurality of items to a plurality of sort destinations and aplurality of delivery vehicles for delivering items to the sortdestinations. The apparatus may include a controller for providingsignals for controlling operation of one of the vehicle carrying one ofthe items to one of the sort destinations. In response to acharacteristic determined for an item the central controller may controlthe operation of the vehicle so that the position of the vehiclerelative to the sort destination varies in response to the determinedcharacteristic.

According to a further aspect, the invention provides sort destinationin the form of an output bin having a rearward end through which theitem is discharged into the output bin.

According to another aspect of the invention an output bin for amaterial handling system may comprise an open rearward end.

According to another aspect of the invention an output bin for amaterial handling system may comprise a displaceable or collapsiblerearward wall.

According to another aspect of the invention a method is provided forsorting a plurality of items. The method may include the step of loadingan item onto a vehicle to be delivered to an output bin and driving thevehicle to the output bin. The method may further include the steps ofdischarging the item from the vehicle into the output bin and monitoringthe position of the item on the vehicle. The method may also include thestep of controlling operation of the vehicle based on the step ofmonitoring the position of the item, wherein the step of controllingoperation of the vehicle comprises controlling the vehicle to attempt tomove the item to a desired location on the vehicle.

According to a further aspect, the invention provides a method includingthe step of driving a vehicle along a guide. The guide may comprise asurface and the vehicle may comprises a rotatable element, so that thestep of driving a vehicle along a guide comprises driving the rotatableelement along the surface of the guide. The step of driving the vehiclemay comprise driving the vehicle in a vertical direction.

According to another aspect, the invention includes a method for sortingitems using a plurality of vehicles, including the step of controllingthe acceleration or deceleration of a vehicle to control the position ofan item on the vehicle.

According to a further aspect of the invention, a method for sortingitems using vehicles includes the step of driving a conveyor belt of thevehicle to displace the item on the vehicle while the vehicle is movingalong a track.

According to another aspect, the invention provides a method for sortingitems using a plurality of vehicles including the step continuouslymonitoring the position of an item on a vehicle as the vehicle travelsto the output bin.

In another aspect, the invention provides an apparatus for sorting aplurality of items that includes a plurality of delivery vehicles guidedby a track to deliver items to one or more destination. The apparatusmay include a loading station for loading items onto the vehicles. Theitems may be analyzed to detect a first characteristic before the itemsare loaded onto a vehicle. A recirculation system may be provided forrecirculating items to an input station from a point along the track.

In another aspect, the invention provides an apparatus for sorting aplurality of items that includes a plurality of delivery vehicles guidedby a track to deliver items to one or more destination and the apparatushaving a qualification station for detecting first and secondcharacteristics of items to be delivered by the vehicles before theitems are loaded onto the vehicles at a loading station. The system mayinclude a recirculation path providing a path along which the items canbe transported along the track. The recirculation path may have a firstend and a second end and the first end may be positioned verticallyhigher than the second end. The second end may be positioned adjacentthe input station so that items placed on the first end of therecirculation pathway tend to move downwardly toward the second endadjacent the input station.

According to another aspect, the invention provides an apparatus forsorting a plurality of items and the apparatus may include a reject areapositioned vertically lower than a first end of a recirculation path.The recirculation path may be a roller bed. The recirculation path maybe a chute or slide. The recirculation path may comprise a conveyorincluding one or more moveable belts or belt links.

According to a further aspect, the invention provides a sortingapparatus having a controller for controlling operation of deliveryvehicles, wherein in response to signals received from by a scanningstation regarding a first characteristic for an item, a vehicle isdirected to an entrance to a recirculation path where the controllercontrols the vehicle to discharge the item onto the recirculation path.The recirculation path may convey the item back to an input station. Atthe input station the item may be re-processed at a qualificationstation. Additionally, in response to signals from the scanning stationregarding a second characteristic the item is directed to a reject area.

According to another aspect of the invention a sorting apparatus isprovided in which in response to signals from a qualification station acontroller controls a vehicle to direct the vehicle to the one of thedestination areas.

According to another aspect, the invention provides a method for sortinga plurality of items that includes scanning items and selectivelyelevating items above an input area based on scanned characteristics.The method may also include the step of selectively conveying items downa re-circulation path to the input area after the step of selectivelyelevating items. The method may include the step of selectively sortingitems after the step of selectively elevating items.

According to another aspect, the method may include the step of movingitems to the input area. The method may also include the step ofscanning the items to detect a first characteristic of the item.Optionally, the system may include the step of scanning the item todetect a second characteristic of the item. The system may include thestep of selectively directing items to a reject area based on the stepof scanning the items to detect a first characteristic or the step ofscanning the items to detect a second characteristic.

According to another aspect, the step of selectively elevating items maybe based on the step of scanning the items to detect a firstcharacteristic or the step of scanning the items to detect a secondcharacteristic. Optionally, the step of selectively conveying items downa re-circulation path may be based on the step of scanning the items todetect a first characteristic or the step of scanning the items todetect a second characteristic. Additionally, the step of selectivelysorting the items to one or more destinations may be based on the stepof scanning the items to detect a first characteristic and the step ofscanning the items to detect a second characteristic.

Systems and methods are described for aiding in the reliable andaccurate sensing of an object boundary such, for example, as the leadingand/or trailing edge surface(s) of an object relative to an underlyingconveyor surface. According to one or more embodiments, a sensingarrangement for sensing an object boundary location relative to anunderlying object support surface comprises a plurality of photodetectorelements disposed in a linear array; a laser light source; and a lenssystem dimensioned and arranged to receive optical energy from the laserlight source and to collimate the received optical energy into a linealigned with the plurality of photodetector elements. Optical energy ofthe line is received by each photodetector element of the plurality ofphotodetector elements unless an amount of optical energy above asensitivity threshold is absorbed, reflected or refracted by an objectdisposed on the underlying support surface.

In another embodiment, a system for conveying objects along a conveyingpath defines an object support surface and includes an object transfermechanism operative to move an object, supported by the object supportsurface, in at least one object transfer direction; and a sensingarrangement for sensing an intersection between an object and adetection plane transverse and a detection plane, the sensingarrangement including a plurality of photodetector elements disposed ina linear array; a laser light source; and a lens system dimensioned andarranged to receive optical energy from the laser light source and tocollimate the received optical energy into a line aligned with theplurality of photodetector elements, wherein optical energy of the lineis received by each photodetector element of the plurality ofphotodetector elements unless an amount of optical energy above asensitivity threshold is absorbed, reflected or refracted by an objectdisposed on the object support surface.

In yet another embodiment, a vehicle for conveying objects along aconveying path in a material handling system comprises first and secondshafts extending in a direction transverse and orthogonal to an objecttransfer direction; a conveyor belt supported by the pair of shafts, theconveyor belt defining an object support surface; an electric motor fordriving at least one of the shafts and causing movement of the conveyorbelt and any object disposed on the object support surface followingmovement of the vehicle along the conveying path to an object transferlocation; a sensing arrangement for sensing an object boundary locationrelative to the object support surface, the sensing arrangementincluding a plurality of photodetector elements disposed in a lineararray; a laser light source; and a lens system dimensioned and arrangedto receive optical energy from the laser light source and to collimatethe received optical energy into a line aligned with the plurality ofphotodetector elements. Optical energy of the line is received by eachphotodetector element of the plurality of photodetector elements unlessan amount of optical energy above a sensitivity threshold is absorbed,reflected or refracted by an object disposed on the object supportsurface.

In some embodiments, a vehicle for conveying objects along a conveyingpath in a material handling system comprises a pair of shafts comprisinga first shaft and a second shaft extending in a direction transverse toan object transfer direction; a conveyor belt supported by the pair ofshafts, the conveyor belt defining an object support surface; anelectric motor for driving at least one of the shafts and causingmovement of the conveyor belt and any object disposed on the objectsupport surface following movement of the vehicle along the conveyingpath to an object transfer location, a first sensing arrangementdisposed adjacent the first shaft for sensing a first object boundaryrelative to the object support surface, and a second sensing arrangementadjacent to second shaft for sensing a second object boundary locationrelative to the object support surface. Each of the first and secondsensing arrangements includes a plurality of photodetector elementsdisposed in a linear array, a laser light source, and a lens systemdimensioned and arranged to receive optical energy from a respectivelaser light source and to collimate the received optical energy into aline aligned with a corresponding plurality of photodetector elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary and the following detailed description of thepreferred embodiments of the present invention will be best understoodwhen read in conjunction with the appended drawings, in which:

FIG. 1 is a perspective view of a material handling apparatus;

FIG. 2 is a plan view of the material handling system illustrated inFIG. 1;

FIG. 3 is a side elevation view of one side of the track of the materialhandling system illustrated in FIG. 2;

FIG. 4 is a perspective view of an alternate induction station for thematerial handling system illustrated in FIG. 1 with a re-circulationsystem;

FIG. 5 is a side view of the material handling apparatus incorporatingthe induction station and re-circulation system illustrated in FIG. 4;

FIG. 6 is a plan view of the material handling system incorporating theinduction station and re-circulation system of FIG. 4;

FIG. 7 is a top perspective view of a delivery vehicle of the apparatusillustrated in FIG. 1;

FIG. 8 is a front view, in elevation, depicting an object sensingarrangement;

FIG. 9A depicts a linear array of photodetector elements and collimatedsource of optical energy mounted on a common support structure andforming part of an object sensing arrangement of the object sensingarrangement of FIG. 8;

FIG. 9B depicts a reflecting mirror forming alignable with the commonsupport structure of FIG. 9A;

FIG. 10A is a front view of an object sensing arrangement detecting anoptically opaque object when the object traverses a detection planedefined by propagation of collimated optical energy in a directiontransverse to an object conveying path;

FIG. 10B is a front view of an object sensing arrangement detecting anobject having at least one light refracting or reflecting portion whilesuch object traverses a detection plane defined by propagation ofcollimated optical energy in a direction transverse to an objectconveying path;

FIG. 11 is a perspective view of an alternate vehicle a materialhandling system; and

FIG. 12 is an electrical schematic depicting a circuit comprisingphototransistors and state sensing logic and operative to signal achange in sensing state when an object traverses the detection plane ofone of the object sensing arrangements of FIGS. 8-11.

DETAILED DESCRIPTION OF THE INVENTION

Some portions of the detailed description which follow are presented interms of operations on binary digital signals stored within a memory ofa specific apparatus or special purpose computing device or platform. Inthe context of this particular specification, the term specificapparatus or the like includes a general purpose computer once it isprogrammed to perform particular functions pursuant to instructions fromprogram software. In this context, operations or processing involvephysical manipulation of physical quantities. Typically, although notnecessarily, such quantities may take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared orotherwise manipulated. It has proven convenient at times, principallyfor reasons of common usage, to refer to such signals as bits, data,values, elements, symbols, characters, terms, numbers, numerals or thelike. It should be understood, however, that all of these or similarterms are to be associated with appropriate physical quantities and aremerely convenient labels. Unless specifically stated otherwise, asapparent from the following discussion, it is appreciated thatthroughout this specification discussions utilizing terms such as“processing,” “computing,” “calculating,” “determining” or the likerefer to actions or processes of a specific apparatus, such as a specialpurpose computer or a similar special purpose electronic computingdevice. In the context of this specification, therefore, a specialpurpose computer or a similar special purpose electronic computingdevice is capable of manipulating or transforming signals, typicallyrepresented as physical electronic or magnetic quantities withinmemories, registers, or other information storage devices, transmissiondevices, or display devices of the special purpose computer or similarspecial purpose electronic computing device.

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Referring now to FIGS. 1-3, an apparatus for sorting items is designatedgenerally 10. The apparatus 10 includes a plurality of delivery vehicles200 that travel along a track system 100 to deliver items to a pluralityof destinations or sort locations, such as output bins 190. Items areloaded onto the vehicles at a loading station 310 so that each vehiclereceives an item to be delivered to a sort location. An inductionsstation 50 serially feeds items to the loading station 310. One or morecharacteristic of each item can be used to control the processing of theitems as the vehicles move along the track 100 to the output bins. Thecharacteristic(s) of each item may be known from each item or thecharacteristic(s) may be acquired by the system as the system processesthe item. For instance, the induction station 50 may include one or morescanning elements for detecting one or more characteristic of the item.

From the loading station 310, the vehicles 200 travel along a track 110to the destinations. The track may include a horizontal upper rail 135and a horizontal lower rail 140, which operates as a return leg. Anumber of parallel vertical track legs 130 may extend between the upperrail and the lower return leg. The bins 190 may be arranged in columnsbetween the vertical track legs 130.

The vehicles 200 are semi-autonomous vehicles that may have an onboardpower source and an onboard motor to drive the vehicles along the track110. The vehicles may include a loading/unloading mechanism 210, such asa conveyor, for loading pieces onto the vehicles and discharging thepieces from the vehicles.

Since the system 10 includes a number of vehicles 200, the positioningof the vehicles is controlled to ensure that the different vehicles donot crash into each other. In one embodiment, the system 10 uses acentral controller 350 that tracks the position of each vehicle 200 andprovides control signals to each vehicle to control the progress of thevehicles along the track. The central controller 350 may also controloperation of the various elements along the track, such as the gates180.

The following description provides details of the various elements ofthe system, including the induction station 50, the track system 100 andthe vehicles 200. The manner in which the system operates will then bedescribed. In particular, the manner in which the items are deliveredmay be controlled based on the characteristics of the items.

Induction Station

At the induction station 50, items are inducted into the system byserially loading items onto the vehicles 200. Since characteristics ofthe items may be used to control the operation of the vehicles, thesystem needs to know the characteristics. In one instance, thecharacteristics may be stored in a central database so that thecharacteristics are known and the system tracks the progress of theitems so that the identification of the item is known as the itemreaches the induction station 50. In this way, since the identificationof the item is known the system 10 can retrieve data regarding thecharacteristics of the item, which are stored in the database.Alternatively, the items are scanned at the induction station 50 toidentify one or more characteristic of each item.

In one embodiment, each item is manually scanned at the inductionstation to detect one or more features of the item. Those features areused to ascertain the identification of the item. Once the item isidentified, various characteristics of the item may be retrieved from acentral database and the item may be subsequently processed based on theknown characteristics of the item. For instance, the induction station50 may include a scanning station 80 that scans for a product code, suchas a bar code. Once the product code is determined, the system retrievesinformation regarding the product from a central database. Thisinformation is then used to control the further processing of the itemas discussed further below.

In a second embodiment, the items are scanned at the induction station50 to detect various physical characteristics of the items. Forinstance, the induction station 50 may measure characteristics such asthe length, height and/or width of an item. Similarly, the weight orshape of the item may be detected. These characteristics may be manuallyor automatically detected at the induction station. For instance, aseries of sensors may be used to detect the length of an item and ascale can be used to automatically weigh an item. Alternatively, anoperator may analyze each item and enter information regarding each itemvia an input mechanism, such as a mouse, keyboard or touchscreen. Forinstance, the system may include a touchscreen that includes one or morequestions or options. One example would be the packaging: is the item ina plastic bag, a blister pack or loose? Is the item flat, cylindrical orround? The system may include default characteristics so that theoperator only needs to identify the characteristics for an element ifthe element has characteristics that vary from the default values. Forinstance, the default characteristic for items may be flat orrectangular. If an item is rounded (e.g. spherical or cylindrical) theoperator inputs information indicating that the item is rounded and theitem is subsequently processed accordingly. Based on the detectedinformation the item is processed accordingly.

As noted above, a variety of configurations may be used for the inputstation, including manual or automatic configurations or a combinationof manual and automated features. In a manual system, the operatorenters information for each item and the system delivers the itemaccordingly. In an automatic system, the input system 50 includeselements that scan each item and detect information regarding each item.The system then delivers the item according to the scanned information.

In an exemplary manual configuration, the input system includes a workstation having a conveyor, an input device, such as a keyboard, and amonitor. The operator reads information on the item, such as an ID tag,inputs information from the tag into the system using the keyboard orother input device and then drops in onto a conveyor. The conveyor thenconveys the piece to the loading station 310. For instance, the operatormay visually read information marked on the item or the operator may usean electronic scanner, such as a bar code reader, to read a bar code orother marking on the item. Sensors positioned along the conveyor maytrack the piece as the conveyor transports the item toward the loadingstation.

Alternatively, as shown in FIGS. 1-4, the induction station 50 mayinclude a scanning station 80 for automatically detectingcharacteristics of the items. Specifically, the induction station 50 mayinclude an input conveyor 55 for receiving items and conveying the itemsto a scanning station 80 operable to detect one or more physicalcharacteristics of an item. From the scanning station 80, a feedconveyor 70 conveys the item to the loading station 310 where the itemis either loaded onto one of the vehicles 200 or passed through to areject bin 325.

The input conveyor 55 may be any of a variety of conveying devicesdesigned to convey items. In particular, the input conveyor may bedesigned to receive items dropped onto the conveyor. For instance, theinput conveyor 55 may be a horizontal conveyor belt or a horizontalroller bed formed of a plurality of generally horizontal rollers thatare driven, thereby advancing items along the conveyor away from theroller.

The input conveyor 55 may be configured so that an operator can selectan item from a supply of items located adjacent the input conveyor. Forexample, a separate supply conveyor may convey a steady stream of itemsto the induction station 50. The operator may continuously select anitem from the supply conveyor and drop the items onto the input conveyor55. Alternatively, a large container of items may be placed adjacent theinput conveyor 55, such as a bin or other container. The operator mayselect items one at the time from the supply bin and place each itemonto the input conveyor. Still further, the input conveyor 55 maycooperate with a supply assembly that serially feeds items onto theinput conveyor. For example, a supply conveyor may convey a continuousstream of items toward the input conveyor 55. The input conveyor mayinclude a sensor for sensing when an item is conveyed away from theinput conveyor. In response, the system may control the operation ofboth the supply conveyor and the input conveyor 55 to drive an itemforwardly from the supply conveyor onto the input conveyor. In this way,items may be fed onto the input conveyor either manually by the operatoror automatically by a separate feed mechanism operable to feed items tothe input conveyor.

Before being loaded onto a vehicle for delivery or sorting, theinduction station may include a scanning station 80 for detecting one ormore characteristic of each item.

Various factors may be detected to evaluate how an item is to beprocessed. For instance, an item typically needs to be identified sothat the system can determine the location or bin to which the item isto be delivered. This is normally done by determining the unique productcode for the item. Therefore, the system may electronically tag an itemas being qualified for sorting if the system is able to identify theitem using a product marking or other indicator. For example, theoperator may read a product identification code on an item and enter theproduct code into the system using an input mechanism, such as akeyboard. If the product code entered by the operator corresponds to aproper product code, then the item may be qualified for sorting.Alternatively, if the operator enters the product code incorrectly or ifthe product code does not correspond to a recognized item, the systemmay electronically tag the item as unqualified.

Similarly, the system may include a scanning element for scanning aproduct identification marking on the product. By way of example, theitems may be marked with one or more of a variety of markings,including, but not limited to, machine-readable optical labels, such asbar codes (e.g. QR or UPC codes), printed alphanumeric characters or aunique graphic identifier. The scanning station 80 may include a scanneror reader for reading such a marking. For instance, a bar code reader,optical reader or RFID reader may be provided to scan the item to readthe identification marking.

The reader may be a hand held device manually manipulatable by theoperator, such as a handheld laser scanner, CCD reader, bar code wand orcamera-based detector that scans an image of the item and analyzes theimage data to attempt to identify the product identification marking. Inthis way, the operator can manipulate the item and/or the detectiondevice to scan the identification marking on the item. Alternatively,the scanner or reader may be a built-in scanner, such as any of theabove-mentioned devices that are built into the induction station sothat the item is simply conveyed over, across or past the built-inreader, which reads the product identification marking. With such adevice, the operator may pass the item over the scanner or the item maybe conveyed past the scanner automatically.

Once the product identification marking is determined (either manuallyor automatically), the system retrieves information regarding theproduct and then controls the further processing of the item based onthe information stored in the central database.

From the foregoing, it can be seen that a variety of different inputmechanisms may be utilized to attempt to determine a productidentification marking on an item. In the present instance, the scanningsystem 80 includes one or more optical readers operable to scan items toobtain optical image data of the item. The system then processes theoptical image data to detect the presence of a product identificationmarking. If a product identification marking is detected, the systemanalyzes the marking to determine the product identification number orcode.

For example, as shown in the embodiments in FIGS. 1-2 and 4, thescanning station 80 may include a plurality of optical imaging elements85, 88, such as digital cameras, positioned along the feed conveyor 70.The imaging elements are spaced apart from one another and disposedaround the feed conveyor so that the imaging elements can scan varioussides of the item as the item is conveyed toward the loading station310. Specifically, the scanning station 80 includes one or more cameras85 directed along a horizontal axis to scan the front and back sides ofthe item. In particular, the scanning station may include a plurality ofimaging elements 85 positioned along a front edge of the feed conveyorand a plurality of imaging elements positioned along a rearward edge ofthe feed conveyor. Additionally, the scanning station 80 may include oneor more cameras 88 directed along a vertical axis to scan the top of theitem as the item is conveyed along the feed conveyor 70. Further still,additional imaging elements may be provided to scan the leading andtrailing faces of an item as the feed conveyor 70 conveys the item.Additionally, the feed conveyor 70 may include a transparent surfacethat the items are conveyed over so that the bottom surface of the itemscan be scanned by the detection station. In this way, the scanningstation may include an array of sensors, reading elements, scanningelements or detectors positioned around a path of movement so that thescanning station can automatically scan an item for an identificationmark while the item is conveyed along the path.

As described above, the scanning station 80 may analyze each item toattempt to find a product identification marking to identify the itembased on the marking. If the product identifier is determined the systemmay then determine the destination for the item and the item may beelectronically tagged as qualified for sorting. Similarly, parametersfor how the item should be handled by the vehicle may also be determinedbased information for the product code stored in a database. Conversely,if the product identifier is not determined for an item, then the itemmay be electronically tagged as not qualified for sorting.

In addition to analyzing the items to find a product marking, thescanning station 80 may incorporate one or more elements operable toevaluate, analyze or measure a physical characteristic of the item todetermine how the item is to be processed. For instance, the scanningstation 80 may include a scale for weighing items. If the detectedweight is greater than a threshold, then the system may electronicallytag the item as requiring certain handling during subsequent processing.For instance, if the weight exceeds a threshold, the system may controlthe subsequent processing to ensure that the item is not discharged intoa destination bin into which a fragile item has been placed.Alternatively, if the weight exceeds a threshold (that may be differentfrom the threshold noted above) the item may be tagged as not beingqualified for sorting. Similarly, the sorting station 80 may include oneor more detectors for measuring a linear measurement for each item. Forinstance, the sorting station may measure the length, width and/orheight of each item. If one of the measurements exceeds a predeterminedthreshold, then the system may electronically tag the item as requiringspecial handling during subsequent processing. The system may use any ofa variety of elements to measure one or more linear dimension(s) of anitem in the scanning station. For instance, the system may use beamsensors (such as an I/R emitter and an opposing I/R detector) to detectthe leading and trailing edges of the item. Based on the known speed ofthe feed conveyor 70, the length of the item can be determined.Similarly, beam sensors can be oriented in a generally horizontalorientation spaced above the feed conveyor a pre-determined height. Inthis way, if the item breaks the beam sensors then the height of theitems exceeds a pre-determined threshold so that the systemelectronically tags the item as not being qualified for sorting.

Further still, the operator may use an input mechanism to identify anitem as being unqualified for sorting due to a physical characteristicexceeding a pre-determined threshold. For instance, a scale may bemarked on the input conveyor 55 and if the operator sees that an item istoo long or too wide or too high, the operator may push a buttonindicating that the item has a physical characteristic that exceeds anacceptable threshold so that the item is electronically tagged as notbeing qualified for sorting. Similarly, a measuring gauge can be used toassess a physical characteristic of the item. One type of measuringgauge is a tunnel or chute 60 having spaced apart sides. If the itemdoes not fit between the walls of the chute the item exceeds theallowable height, length or width and is electronically tagged as notbeing qualified for sorting.

As described above, the scanning station 80 may be configured to analyzeeach item to detect various characteristics of the items as the itemsare passed through the induction station. The system may make aqualification decision based on one or more of the characteristicsdetected or determined by the system. If the item is not qualified forsorting, then the item may be directed to the reject area 325 to awaitfurther processing.

Typically, items that are directed to the reject area 325 aresubsequently processed manually. An operator takes each piece,identifies the piece and transports the item to the appropriatedestination. Since the manual processing of rejected items istime-consuming and labor intensive, it is desirable to reduce the numberof items directed to the reject area. Many of the items directed to thereject area 325 may simply have been mis-scanned. Although the itemscannot be sorted without sufficient identification information, it maybe possible to read the necessary information during a subsequent scan.

Since it may be desirable to re-process some non-qualified items, theinformation detected during the qualification can be used to identifydifferent categories of non-qualified items. A first type ofnon-qualified item is a reject item that is directed to the reject area.In the following discussion, these items will be referred to as rejecteditems. A second type of non-qualified item is one that is not qualifiedfor sorting but is qualified to be re-processed. In the followingdiscussion, these items will be referred to as reprocess items.

The decision on whether an item is tagged as reject, reprocess or sortcan be made based on a variety of characteristics. In the presentinstance, the decision to tag an item as a reject is based on a physicalcharacteristic of the item. Specifically, if an item fails to qualifydue to a physical characteristic (e.g. has a linear dimension such asheight, width or length that exceeds a threshold), the systemelectronically tags the item as rejected and the item is directed to thereject area 325 for manual processing. Similarly, if the scanningstation includes a scale, an item is tagged as rejected if the weightexceeds a weight threshold. On the other hand, if an item passesqualification based on the physical characteristics, but fails due to aninability to identify a product identification element, then the elementis electronically tagged as reprocess so that the item can bereprocessed to attempt to read the product identification information.For instance, depending on the orientation of the product, the imagingelements 85, 88 may have been unable to properly read a bar code orother identifying mark. However, since the scanning station hasdetermined that the item meets the physical parameters for processingthe item, the system may transport the item to an alternate output, suchas a bin for receiving items to be re-processed. Items sorted ortransported to the re-processing bin may be manually returned to theinduction station 50 so that the operator can input the items anew.Alternatively, the system may transport such items through the system toa re-induction assembly that returns the item to the entry conveyor 55of the induction station 50.

In this way, the system 10 is operable to analyze an item to determineone or more of characteristics of the item and determine whether theitem is qualified for transportation or if the item needs to be shuntedaway to ensure that the item is not conveyed through the system by avehicle. By doing so, the system is able to minimize damage to the itemsor the system that can occur if oversized or overweight items aretransported or attempted to be transported along the track 110 by one ofthe vehicles 200. Further still, if an item is qualified fortransportation, but fails to be qualified for sorting, the item can betransported to a re-induction station to attempt to re-process the itemas discussed further below.

As can be seen from the foregoing, the induction station 50 may beconfigured in a wide range of options. The options are not limited tothose configurations described above, and may include additionalfeatures.

Additionally, in the foregoing description, the system is described ashaving a single induction station 50. However, it may be desirable toincorporate a plurality of induction stations positioned along thesystem 10. By using a plurality of induction stations, the feed rate ofpieces may be increased. In addition, the induction stations may beconfigured to process different types of items.

Referring to FIGS. 1-3, the induction station 50 includes a feedconveyor 70 that serially conveys items to a loading station 310. Theloading station is a location along the track 110 that provides an entrypoint for loading an item onto a vehicle 200. At the loading station 310the vehicle is aligned with the feed conveyor 70 so that itemsdischarged from the feed conveyor are received onto the delivery vehicle200 positioned at the loading station. After the item is loaded onto thedelivery vehicle, the delivery vehicle moves away from the loadingstation 310 if the item is electronically tagged as being qualified fortransport. Another vehicle then moves into position at the loadingstation to receive the next item. If the item is not electronicallytagged as being qualified for transport, the item is discharged from thevehicle 200 into the reject bin 325.

The reject bin 325 is positioned so that it opposes the feed conveyor 70of the induction station 50. Additionally, the reject bin 325 is alignedwith the vehicle 200 waiting at the loading station 310. In this way, aclear pathway is provided from the induction station 50 to the rejectbin 325 without requiring movement of the vehicle along the track 110.

Re-Induction Assembly

Referring to FIGS. 4-6, an alternate embodiment of the system isillustrated in which the system includes an optional re-induction systemfor items that were qualified for transport but not qualified forsorting. In FIGS. 4-5, details of the inductions station 50 andre-induction system are illustrated without the details of the sortingstation 100, such as the output bins 190 and the track system 110. Itemsthat are qualified for transport may be transported away from theloading station 310 to either a re-induction station or to the sortingstation 100. Specifically, a vehicle carrying an item qualified fortransport moves upwardly along the track 110 to the upper rail 135. Ifthe item on the vehicle is tagged as re-assess, then the vehicle drivesalong the track to the re-induction station 430. The vehicle 200 thendischarges the item onto the re-induction assembly 410, which conveysthe item back toward the induction conveyor so that the item can bere-processed through the induction assembly in an attempt to qualify theitem for sorting.

The re-induction assembly 410 comprises a pathway between the track andthe induction station 50 to facilitate return of re-assess items to theinduction station. The re-induction assembly 410 may comprise any of anumber of conveyance mechanisms. The mechanisms can be driven or static,motorized or un-motorized. However, in the present instance, there-induction assembly 410 comprises a roller bed 440 that is angleddownwardly so that items tend to roll along the roller bed.Specifically, the roller bed 440 has an upper end at the re-inductionstation 430. The re-induction station 430 is positioned verticallyhigher than the lower end of the roller bed 440 so that gravity tends toforce the item along the roller bed when the item is discharged at theupper end of the roller bed at the re-induction station.

The re-induction assembly 440 includes edge guides 450 that projectupwardly from the edges of the roller bed and extend along the edges ofthe roller bed. A transverse wall extends across the lower edge of theroller bed 440 between the edge guides, thereby forming an end wall 460to retain items from rolling off the end of the roller bed 440. One ofthe edge guides 450 has a terminal edge spaced apart from the end wall460 thereby forming an access opening 455 at the end of the roller bed.

The re-induction assembly 410 extends from the track 110 to an areaadjacent the induction station 50. Specifically, the end of there-induction assembly is positioned adjacent the input conveyor 55 andmore specifically is positioned so that an operator at the inputconveyor can readily access items at the access opening 455 on theroller bed 440.

The induction station 50 may include a secondary scanning element usedto scan items being re-processed. For instance, as described above, thescanning station 80 may include an array of imaging elements that scanthe item to obtain image data. The image data is then analyzed to detectthe presence of a product identification marking. The induction station50 may also include a portable laser bar code scanner that the operatorcan use to scan a bar code on the item during re-processing. In thisway, a first detection element is used during the first processing and asecond detection element is used during the re-processing.

The induction station 50 may also include an input mechanism that theoperator can operate to indicate that an item is being re-processed. Forinstance, the operator may press a button before dropping an item ontothe input conveyor 55 from the re-induction assembly 410. The system maythen tag the item as being previously processed so that if the system isunable to validate the item for processing on a second attempt the itemis tagged as a reject rather than being tagged again as re-assess. Inthis way, items that have a flaw that prevents identification do notcontinue to loop through the re-induction assembly 410. Similarly, if asecondary scanning element is used during re-processing, the use of thesecondary scanning element can serve as a signal that the item is beingre-processed. In other words, the system may tag the item as beingre-processed when the secondary element is used to scan an item.

As described above, the re-induction assembly comprises a roller bed 440that uses gravity to convey items back to the induction station 50. Itshould be understood that alternative mechanisms could be used ratherthan a roller bed. For instance, a chute or flat slide may be used.Alternatively, a conveyor belt could be incorporated to drive the itemstoward the induction station. Additionally, in the above description there-induction assembly 410 is a generally straight path. However, itshould be understood that the re-induction assembly my incorporate aturn or angle so that the discharge end of the re-induction assembly ispositioned adjacent the input conveyor 55 of the induction station.Further still, in FIGS. 4-5 and the above description, the re-inductionstation 430 is located in the column next to the loading column 300.However, it should be understood that the re-induction station 430 andthe accompanying conveyor 440 may be located in other columns, includingthe loading column 300.

Sorting Station

Items that are qualified for sorting by the induction station 50 areconveyed by vehicles to the sorting station. Referring to FIGS. 1-6, thesystem includes a sorting station 100, such as an array of bins 190 forreceiving the pieces.

The track 110 includes a horizontal upper rail 135 and a horizontallower rail 140. A plurality of vertical legs 130 extend between theupper horizontal leg and the lower horizontal leg 140. During transport,the vehicles travel up a pair of vertical legs from the loading station310 to the upper rail 135. The vehicle then travels along the upper railuntil reaching the column having the appropriate bin or destination. Thevehicle then travels downwardly along two front vertical posts and twoparallel rear posts until reaching the appropriate bin or destination,and then discharges the item into the bin or destination area. Thevehicle then continues down the vertical legs until reaching the lowerhorizontal leg 140. The vehicle then follows the lower rail back towardthe loading station.

The track 110 includes a front track 115 and a rear track 120. The frontand rear tracks 115, 120 are parallel tracks that cooperate to guide thevehicles around the track. As shown in FIG. 7, each of the vehiclesincludes four wheels 220: two forward wheel 220A and two rearward wheels220B. The forward wheels 220A ride in the front track, while therearward wheels 220B ride in the rear track. It should be understoodthat in the discussion of the track, the front and rear tracks 115, 120are similarly configured opposing tracks that support the forward andrearward wheels 220A, 220B of the vehicles. Accordingly, a descriptionof a portion of either the front or rear track also applies to theopposing front or rear track.

Referring now to FIGS. 1-3 a loading column 300 is formed adjacent theoutput end of the induction station 50. The loading column 300 is formedof a front pair of vertical rails 305 a, 305 b and a correspondingrearward set of vertical rails. The loading station 310 is positionedalong the loading column. The loading station 310 is the position alongthe track in which the vehicle 200 is aligned with the discharge end ofthe feed conveyor 70 of the induction station 50. In this way, an itemfrom the induction station may be loaded onto the vehicle as it isconveyed toward the vehicle from the input station.

The details of the track are substantially similar to the track asdescribed in U.S. Pat. No. 7,861,844. The entire disclosure of U.S. Pat.No. 7,861,844 is hereby incorporated herein by reference.

As described above and referring to FIG. 3, the track includes aplurality of vertical legs extending between the horizontal upper andlower rails 135, 140. An intersection is formed at each section of thetrack at which one of the vertical legs intersects one of the horizontallegs. Each intersection includes a pivotable gate that has a smoothcurved inner race and a flat outer race that has teeth that correspondto the teeth of the drive surface for the track. The gate pivots betweena first position and a second position. In the first position, the gateis closed so that the straight outer race of the gate is aligned withthe straight outer branch of the intersection. In the second position,the gate is open so that the curved inner race of the gate is alignedwith the curved branch of the intersection.

In the foregoing description, the sorting station 100 is described as aplurality of output bins 190. However, it should be understood that thesystem may include a variety of types of destinations, not simply outputbins. For instance, in certain applications it may be desirable to sortitems to a storage area, such as an area on a storage shelf.Alternatively, the destination may be an output device that conveysitems to other locations.

The output bins 190 may be generally rectilinear containers having abottom, two opposing sides connected to the bottom, a front wallconnected to the bottom and spanning between the two sides. The bin mayalso have a rear wall opposing the front wall and connected to thebottom and spanning the two sides. In this way, the bin may be shapedsimilar to a rectangular drawer that can be pulled out from the sortingstation to remove the items from the bin.

The bins in a column are vertically spaced apart from one another toprovide a gap between adjacent bins. A larger gap provides moreclearance space for the vehicles to discharge items into a lower binwithout the bin above it interfering with the item. However, a largergap also decreases the number of bins or the size of bins (i.e. the bindensity). Therefore, there may be a compromise between the size of thegap and the bin density.

The vehicles 200 discharge items into the bins through the rearward endof the bin. Therefore, if the backside of the bin is open the vehiclecan readily discharge an item into the bin through the rearward open endof the bin. However, if the bin does not have a rearward end the itemsmay tend to fall out of the bin when the bin is withdrawn from the sortrack. Accordingly, depending on the application, the bin may have anopen rearward end or a closed rearward end. If the rearward end isclosed, the rear wall may be the same height as the forward wall.Alternatively, the rear wall may be shorter than the forward wall toprovide an increased gap through which the items may be discharged intothe bin. For instance, the rear wall may only be half the height of theforward wall. Optionally, the rear wall may be between one quarter andthree quarter the height of the forward wall. For instance, the rearwall may be between one half and three quarters the height of theforward wall. Alternatively, the rear wall may be between one quarterand three quarter the height of the forward wall.

Alternatively, rather than having a fixed rear wall, the bins 190 mayhave moveable or collapsible rear walls. For instance, the rear wall ofthe bin may be displaceable vertically relative to the bottom of thebin. In particular, the rear wall may be displaceable by pressing thewall downwardly. The rear wall may be displaceable within grooves orslots formed in the side walls of the bin so that pressing the rear walldownwardly causes the rear wall to be displaced downwardly so that aportion of the rear wall projects below the bottom of the bin. In suchan embodiment, the rear wall may be biased upwardly by a biasingelement, such as a spring, so that the rear wall tends to remain in anupward position with the bottom edge of the rear wall above the bottomedge of the bin. The rear wall only moves downwardly in response to aforce on the rear wall that exceeds the upward biasing force.

Yet another alternative bin incorporates a collapsible rear wall. Likethe displaceable wall, the collapsible wall moves downwardly by pressingdownwardly against the collapsible wall. The collapsible wall may beformed in a variety of configurations, such as an accordion or pleatedconfiguration so that the wall folds downwardly when the wall is presseddownward. The collapsible wall may include a biasing element biasing thewall upwardly to an extended position. For instance, the biasing elementmay include one or more springs or elastomeric elements biasing the wallupwardly to the extended position.

As discussed above, the system is operable to sort a variety of items toa plurality of destinations. One type of destination is a bin; a secondtype is a shelf or other location on which the item is to be stored; anda third type of destination is an output device that may be used toconvey the item to a different location. The system may include one ormore of each of these types or other types of destinations.

Delivery Vehicles

Each delivery vehicle 200 is a semi-autonomous vehicle having an onboarddrive system, including an onboard power supply. Each vehicle includes amechanism for loading and unloading items for delivery. An embodiment ofa vehicle that may operate with the system 10 is illustrated anddescribed in U.S. Pat. No. 7,861,844, which is incorporated herein byreference. However, an alternate vehicle 200 is illustrated in FIG. 8.The vehicle includes additional sensors for detecting characteristics ofthe item being delivered.

The vehicle 200 may incorporate any of a variety of mechanisms forloading an item onto the vehicle and discharging the item from thevehicle into one of the bins. Additionally, the loading/unloadingmechanism 210 may be specifically tailored for a particular application.However, in the present instance, the loading/unloading mechanism 210 isone or more conveyor belts that extend along the top surface of thevehicle. The conveyor belts are reversible. Driving the belts in a firstdirection displaces the item toward the rearward end of the vehicle;driving the belt in a second direction displaces the item toward theforward end of the vehicle.

A conveyor motor mounted on the underside of the vehicle drives theconveyor belts 212. Specifically, the conveyor belts 212 are entrainedaround a forward roller at the forward edge of the vehicle, and arearward roller at the rearward edge of the vehicle. The conveyor motoris connected with the forward roller to drive the forward roller,thereby operating the conveyor belts.

The vehicle includes four wheels 220 that are used to transport thevehicle along the track 110. The wheels 220 are mounted onto twoparallel spaced apart axles 215, so that two or the wheels are disposedalong the forward edge of the vehicle and two of the wheels are disposedalong the rearward edge of the vehicle.

Each wheel 220 comprises an outer gear that cooperates with the drivesurface of the track. The outer gear is fixed relative to the axle ontowhich it is mounted. In this way, rotating the axle operates to rotatethe gear. Accordingly, when the vehicle is moving vertically the gearscooperate with the drive surface of the track to drive the vehicle alongthe track.

The vehicle includes an onboard motor for driving the wheels 220. Morespecifically, the drive motor is operatively connected with the axles torotate the axles 215, which in turn rotates the gears 222 of the wheels.

As the vehicle travels along the track, an item on top of the vehiclemay tend to fall off the vehicle, especially as the vehicle acceleratesand decelerates. Therefore, the vehicle may include a retainer to retainthe element on the vehicle during delivery. The retainer may be a holddown that clamps the item against the top surface of the vehicle. Forinstance, the retainer may include an elongated pivotable arm. A biasingelement, such as a spring, may bias the arm downwardly against the topsurface of the retainer.

Alternatively, rather than using a retainer, the system may retain theitem on the vehicle 200 by controlling the operation of the vehicle. Forinstance, the vehicle 200 may include a plurality of sensors 230 spacedapart from one another across the width of the vehicle. In theembodiment illustrated in FIG. 7, the sensors 230 are spaced apart alonga wall 231 at the leading edge of the vehicle. The wall may be anelongated element that extends the width of the vehicle. The walloperates as a stop or constraint, limiting items from falling off orbeing discharges from the leading edge of the vehicle. Similarly, thevehicle 200 may include a trailing wall 232 that may extend the width ofthe vehicle. The trailing wall 232 may operate as a stop or constraint,limiting items from falling off or being discharged from the trailingedge of the vehicle. The vehicle may also include a plurality of sensorelements spaced apart from one another along the trailing wall 232similar to the sensors 230 shown on the leading wall 231 in FIG. 7. Thesensors 230 may be any of a variety of sensors, including, but notlimited to photoelectric sensors (such as opposed through beam sensorsor retroreflective sensors) or proximity sensor (such as capacitive,photoelectric or inductive proximity sensors). The sensors can be usedto detect the location of the item across the width of the vehicle.Specifically, the sensors can detect how close the item is to the frontside 234 or the rear side 236 of the vehicle. Similarly, if the sensors230 are proximity sensors, the sensors can detect how close the item isto the leading edge (i.e. leading wall 231) of the vehicle and/or thetrailing edge of the vehicle (i.e. trailing wall 232). Further still,the sensors can detect movement of the item on the vehicle so that thesystem can detect the direction that the item is moving if the item ismoving on the vehicle.

Based on signals from the sensors 230 regarding the position or movementof the item on the vehicle 200, the system can control the vehicle tore-position the item to attempt to maintain the item within a desiredlocation on the vehicle. For instance, it may be desirable to maintainthe item generally centered on the top of the vehicle. The system cancontrol the position of the item on the vehicle using any of a varietyof controls. For instance, as noted previously, the vehicles 230 mayinclude one or more conveyor belts for loading and discharging items. Insuch a configuration, the item rests on the belts, so the belts areoperable to drive the items toward the forward edge 234 or the rearwardedge 236 depending on signals received from the sensors. In one example,if the signals from the sensors indicate that the item is shifted closerto the rearward edge than the forward edge, the controller can send asignal to the motor driving the belt so that the belt drives in a firstdirection to drive the item toward the forward edge 234. Similarly, ifthe signals from the sensors indicate that the item is shifted closer tothe forward edge than the rearward edge, the controller can send asignal to the motor driving the belt so that the belt drives in a seconddirection to drive the item in the opposite direction to drive the itemtoward the rearward edge 236. The sensors provide continuous feedback sothat the position of the item can be continuously monitored and adjustedtoward the forward edge or toward the rearward edge as the item shifts.In this way, the system provides a feedback loop for providing real-timeadjustment of the position of the item to retain the item within adesired area on the top of the vehicle.

Additionally, the system can monitor the location of the item relativeto the leading and trailing edges of the vehicle (such as walls 231,231). In response to the detected location of the element, the systemcan control the operation of the vehicle if the item is too close to theleading edge or too close to the trailing edge. Specifically, the systemmay control the acceleration and braking of the vehicle to attempt toshift the item toward the leading or trailing edge depending on thedetected position. If the sensors 230 detect that the item is positionedcloser to the leading edge than the trailing edge, the vehicle may beaccelerated (or the acceleration may be increased), thereby urging theitem toward the trailing edge. Alternatively, the vehicle may bedecelerated to urge the item toward the leading edge.

In addition to verifying or monitoring the position of an item on thevehicle, the sensors can be used to detect one or more characteristic ofthe item. For instance, the sensors can be used to detect the length ofwidth of the item. The sensors may also be used to detect the generalshape of the item. This information can be used during furtherprocessing of the item as discussed further below.

As discussed above, the bins 190 may include a rearward wall that isdisplaceable or collapsible. Accordingly, the vehicles may include amechanism for applying a downward force on the rearward wall sufficientto overcome a biasing force retaining the wall in an upper or uprightposition. For instance, the vehicle may include an extendable elementsuch as a pin or rod. When the vehicle approaches the target deliverybin the pin may be extended transversely, away from the vehicle so thatthe pin extends over the rearward wall of the target bin. As the vehiclenears the bin the extended pin engages the upper edge of the rear wallof the bin. Driving the vehicle downwardly drives the pin downwardlyagainst the rearward wall. The system may control the vertical positionof the vehicle to control how far the vehicle pushes down or collapsesthe rear wall. After the vehicle discharges the item into the bin, theextendable element may be retracted, thereby releasing the rear wall sothat the biasing element displaces the rear wall upwardly into the upperposition.

The vehicle 200 may be powered by an external power supply, such as acontact along the rail that provides the electric power needed to drivethe vehicle. However, in the present instance, the vehicle includes anonboard power source that provides the requisite power for both thedrive motor and the conveyor motor. Additionally, in the presentinstance, the power supply is rechargeable. Although the power supplymay include a power source, such as a rechargeable battery, in thepresent instance, the power supply is made up of one or moreultracapacitors.

As discussed further below, the vehicle further includes a processor forcontrolling the operation of the vehicle in response to signals receivedfrom the central processor. Additionally, the vehicle includes awireless transceiver so that the vehicle can continuously communicatewith the central processor as it travels along the track. Alternatively,in some applications, it may be desirable to incorporate a plurality ofsensors or indicators positioned along the track. The vehicle mayinclude a reader for sensing the sensor signals and/or the indicators,as well as a central processor for controlling the operation of thevehicle in response to the sensors or indicators.

Edge-Sensing System

As described above, the system 10 may include one or more elements fordetecting an item on the vehicle. It also may be desirable to detect theleading and trailing edges of an item when the item is loaded onto avehicle or discharged from the vehicle. Accordingly, each vehicle mayinclude one or more sensors to detect items on the vehicle.

In the embodiment illustrated in FIG. 7, each vehicle may include aplurality of detectors 230 that detect items on the top of the vehicle(i.e. on the surface of the belt 212). One of the sensors 230A may bepositioned near the front edge 234 to detect the items as the items areloaded onto or discharged from the front edge. Similarly, one of thesensors 230B may be positioned adjacent the rear edge 236 to detectitems as the items are loaded onto or discharged from the rear edge. Forinstance, the leading sensor 230A may be a beam break sensor so thatwhen an item passes in front of the beam the beam is interrupted. Whenan item is loaded onto the vehicle 200, the leading edge of the itemwill interrupt the beam, thereby indicating that the ledging edge of theitem is on the vehicle. The item may continue to block the lead sensor230A until the trailing edge of the item passes the lead sensor 230A.After the trailing edge of the item passes the lead sensor 230A, thelead sensor will no longer detect the item, thereby indicating that theitem is loaded onto the vehicle. After the trailing edge passes the leadsensor 230A, the conveyor 212 may continue to drive the item toward therear edge 236 to ensure that the item is centered along the width of thevehicle. Similarly, the lead sensor 230A may detect the leading andtrailing edges of the item as the item is discharged from the front 231of the vehicle. Detection of the trailing edge passing the front sensor230A can be used to signal that the item has been discharged from thevehicle. The vehicle is then prompted to advance away from the dischargelocation. The description above of the use of the lead sensor 230A todetect the leading and trailing edges of items being loaded onto ordischarged from the front edge applies similar to the use of the rearsensor 230B in detecting the leading and trailing edges of an item asthe item is loaded onto or discharged from the rear edge of the vehicle.

In the foregoing description, the sensors 230 detect items being loadedonto and being discharged from the front edge 234 or rear edge 236 ofthe vehicle. In certain applications it may be desirable to incorporatea sensing assembly that provides for detection for a greater variety ofitems. For instance, when using a beam break sensor it may be difficultto detect the leading or trailing edge of the item if the item is verythin or if the item is transparent or translucent. Accordingly, thesystem may incorporate an alternate sensing arrangement designated 500and illustrated in FIGS. 8-12. Although the sensing arrangement isdescribed in connection with a vehicle of the material handling system10, it should be understood that the sensing arrangement 500 mayincorporated into other aspects of the system, such as detecting a itemas it passes along through the induction station. Further still, thesensing arrangement 500 described below may find further application infields of endeavor outside the material handling field, including, butnot limited to fields such as mail processing or document processing.

Embodiments of the edge sensing assembly include a system and method foraiding in the reliable and accurate detection of an event such as thetraversal of a detection plane by the leading and/or trailing edgesurface(s) of an object supported by an underlying conveyor surface.According to one or more embodiments, the detection plane is defined byoptical energy, emitted by a laser and collimated by a lens system toform a diverging, constant width beam propagating within the detectionplane. A linear array of photodetectors is maintained in alignment withthe lens system such that the collimated optical energy will strike, ata non-normal angle of incidence, any object which crosses the detectionplane.

Conventional “cross-beam” sensors may have a difficult time detectingclear objects, thin objects and/or irregular shaped objects. Inaccordance with one more embodiments consistent with the presentdisclosure, however, such objects are readily sensed by a change in theintensity of the optical energy detected by one or more of thephotodetectors in the array. For example, if an optically opaque objectis present, optical energy will be absorbed such that at least one ofthe photodetectors senses a drop in optical intensity. Alternatively,for an object that includes portions and/or packaging which is opticallytransparent, some light may pass and some may be reflected or refractedsuch that at least one of the photosensors senses a less pronounced, butnonetheless detectable, drop in optical intensity. Even relatively thin(on the order of 0.05 mm) objects may be reliably detected with anappropriate arrangement of the lens system and photodetectors.

Various embodiments of systems and methods for detecting traversal of adetection plane by the leading and/or trailing edge surface(s) of anobject supported by an underlying conveyor surface are described. In thefollowing detailed description, numerous specific details are set forthto provide a thorough understanding of the claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, methods, apparatuses or systems that would be known by one ofordinary skill have not been described in detail so as not to obscureclaimed subject matter.

The edge detecting assembly 500 includes one or more emitters 504 foremitting a source of light and one or more detectors 506 for detectingthe emitted light. At least one emitter 504 is positioned below thesurface S on which the item is supported. For example, in the embodimentillustrated in FIG. 10, the emitter 504 is vertically spaced from theplace of surface S so that the emitter is below the plane of surface S.In this example, the plane of surface S is a horizontal plane and theemitter is under the surface. In this way, light emitter from emitter504 projects upwardly at an angle relative to the plane of surface S. Byprojecting the emitted light at an angle relative to surface S, theobject may have a larger surface to impinge the emitted light than ifthe light is emitted parallel to the surface S. For instance, in theexample of a piece of paper laying on surface S, if the light from theemitter is projected parallel to surface S, then only the side edge ofthe paper will reflect or block emitted from the emitter. Since the sideedge of the paper is so thin (such as 0.05 mm) it would be difficult orimpossible to detect using an emitter that projects light parallel tosurface S. However, by lower the emitter to a position below S andprojecting the light at an angle relative to surface S, then entirewidth of the paper may reflect light from the emitter.

Turning now to FIG. 8, the object sensing assembly 500 is adapted tosense when a boundary surface of an object (e.g., the leading edge ortrailing edge of object disposed on an underlying object supportsurface) has crossed into a detection plane or “curtain” 502 of lightemitted by an emitter 504, also referred to as an emitter. A lineararray of photodetector elements 506, indicated generally at 508, isaligned with the emitter 504 so that the emitted light strikes each ofthe photodetectors with undiminished intensity unless an object isinterposed into the detection plane 502.

In some embodiments, the emitter 504 is a solid state laser that emits abeam of coherent light within the range of wavelengths visible to thehuman eye. For efficient and reliable detection of its output, theemitter 504 may be a laser which emits light at or near the peaksensitivity of the photodetectors 506. According to one embodiment, thephotodetectors are phototransistors which, by way of example, may have aspectral range of sensitivity within a range of frequencies between 350to 950 nm and a sensitivity peak of 560 nm. One such phototransistor isthe SFH3710 manufactured by Osram Opto Semiconductors GmbH ofRegensburg, Germany. It should be noted, however, that otherphotodetectors such, for example, as photodiodes, may be employed inplace of phototransistors. The effects of ambient light on photodetectorsensitivity may be addressed, if appropriate, by placing a bandpassfilter over the array 508 to prevent light outside a narrow rangecentered around the sensitivity peak from reaching the photodetectors.

The emitter 504 may comprise a single laser having an integral lenssystem including one or more collimating lenses as lens 522. The lens522 is dimensioned and arranged to receive optical energy emitted by thelaser source and to collimate the received optical energy such that thelight beam diverges within the curtain 102 along a major axis but doesnot diverge along a minor axis. As seen in FIGS. 8 and 9A takentogether, the collimated output of the emitter 504 propagates withincurtain 102 and forms a line or area 550 spanning each photodetector 506of the linear array 508. Even thin and optically transmissive (e.g.translucent) or highly reflective objects can be detected if thecollimated output of the optical source 504 strikes the object at anoblique angle and the photodetectors are spaced from one another andlocated at an elevation relative to where light enters and/or isreflected by the object.

For example, from the perspective of FIG. 8, using a light curtain 502having a width of approximately 25-35 cm wide and a height ofapproximately 10 to 20 cm the assembly can detect an object having athickness of between 0.05 mm (i.e. the thickness of a single sheet ofpaper) to about 10 cm and a width on the order of about 7.5 cm to about30.5 cm. Such detection can be achieved with a 1 mW laser havingintegrated collimating optics. With a fan angle of 20 degrees and a beamdivergence of less than 2 milliradians (mRads), such a laser can projecta 5 cm line having a width of 1-2 mm. When placed adjacent to, butslightly below, a discharge end of an object support surface, theoptical source 504 and array 508 form a detection plane which istransverse and orthogonal to the plane defined by the object supportsurface. In some embodiments, the object support surface may be themoving surface of a conveyor belt. In other embodiments, the objectsupport surface may be a stationary or tilting table surface.

Depending on the components forming the collimating lens system, theintensity of light within line 550 in FIG. 9A may be uniform across allphotodetectors 506 when no object is present to interfere with theintegrity of the light curtain 502. Alternatively, the intensity acrosslight curtain 502 may vary according to a Gaussian or other predictabledistribution function. In either case, embodiments consistent with thepresent disclosure are configured to detect a change in opticalintensity received at any of photodetectors 506 when an object crosses(or leaves) the light curtain 102. That is, when an amount of opticalenergy above a sensitivity threshold is absorbed, reflected or refractedby an object on surface S, the output of at least one of thephotodetectors 506 of array 508 will signal a change in state.

In an illustrative example where the sensing arrangement 500 forms partof a material handling system, a detected change of photodetector statemay be used to confirm the successful transfer of an object into astorage or packing location, successful retrieval of an object from astorage location or picking location. Conversely, the failure to detecta signal indicative of a change in state may also be used to control anoperation in a material handling or other system. For example, after apredetermined “timeout” interval, failure to register a change of statemay be used as part of an alert sequence (e.g., to trigger an audible orvisual alert to a human operator).

One possibility for increasing the coverage of the light detected by thedetectors 506 would be to use a complementary pair of photodetectorarrays and optical sources so as to increase the coverage of the lightcurtain. In the arrangement of FIG. 8, however, it will be seen that areflecting mirror 516 may be used to fold the optical path and therebyobtain comparable results. In such arrangements, the photodetectorelements 506 of array 508, together with the emitter 504, may beoptionally mounted to a first rigid support 510 to form an integratedemitter/detector assembly 512. A reflecting mirror 516 may be mounted toa second rigid support 518. The first and second supports 510, 518 maybe rigidly connected, such as by a support shaft 520 extending betweenthe two supports. The shaft 520 may be resiliently biased to maintainthe orientation of the light curtain 502 relative to the surface S,while also permitting transient angular reorientation of the lightcurtain in response to translation of surface S.

In some embodiments, the photodetector elements 506 and optical source504 may be mounted on a common substrate 524 such, for example, as aprinted circuit board. The collimated, diverging beam emitted by lens522 of emitter 504 is reflected by the surface 530 (FIG. 9B) of mirror516 and forms a projected line or area 550 over the array 508 ofphotodetectors 506. In an exemplary application, where objects to beprocessed are expected to have heights which may vary from less than onemm up to 20 cm or more, line 550 may have a width W, for example, on theorder of from about one to about five mm wide and a length L, forexample, on the order of 10 to 20 cm long. In an exemplary embodiment,the array 508 is arranged to provide coverage over the entire length ofthe line L.

To accommodate the detection of very thin objects, those photodetectors506 of the array closer to the object support surface S may be moreclosely spaced than those further away from the object support surface.In the exemplary embodiment of FIG. 9A, the spacing d₁ among the lowestfour photodetectors may be on the order of 1-5 mm while the spacing d₂among the remaining photodetectors is on the order of 10-15 mm. Ofcourse, such an arrangement is described herein by way of illustrativeexample only. Also contemplated herein are arrangements such as those inwhich the inter-photodetector spacing among at least a subset of thephotodetectors increases monotonically with distance from the objectsupporting surface, and/or arrangements in which a uniforminter-photodetector spacing is used. It suffices to say that the numberand spacing of the photodetectors may be varied without departing fromthe spirit and scope of the present disclosure.

FIG. 9B depicts a reflecting mirror mounted on an arm 518 and alignablewith the support 510 of FIG. 9A to form an object sensing arrangement512 such as the one depicted in FIG. 8. As seen in FIG. 9B, the mirror516 defines a substantially planar reflecting surface 530 and is affixedto second rigid member 518. Additionally, as shown in FIGS. 8, 9A and9B, the height of the curtain of light impinging mirror 516 issubstantially less than the height (L) of the array 508. Accordingly,the height of the mirror 516 may be substantially less than the height(L) of the array 508.

A transverse bore 526 a and 526 b may be defined in each of first rigidmember 510 and second rigid member 518 to accommodate insertion of anoptional mounting shaft such as mounting shaft 520 (FIG. 8). Inoperating environments in which the sensing arrangement is secured to astationary structure such, for example as the frame of a conventionalbelt or roller conveyor, the mounting shaft and corresponding transversebores 526 a and 526 b may be omitted. Alternatively, or in addition,some other structure for aligning the optical source, photodetectors andreflecting mirror (if applicable) relative to one another and to anobject support surface may be employed.

FIG. 10A depicts use of a sensing arrangement such as the one depictedin FIG. 8 to detect an optically opaque object O₁ as the object movesalong an object conveying path (e.g., upon an underlying support surfaceS) and traverses a light curtain (or “detection plane”) that is definedby propagation of collimated optical energy in a direction transverse tothe object conveying path. As seen in FIG. 10A, light emitted by opticalenergy source 504 is collimated by a lens structure which includes lens522. In this example, the height and width of object O₁ are such thatlight from emitter 504 is reflected from mirror 516 and detected bydetectors 506-2 through 506-10. However, object O₁ absorbs most or allof the optical energy that would have reached photodetector 506-1, sothat detector 506-1 does not detect light or the light detected bydetector 506-1 is below a threshold.

As explained in greater detail below, the reduction in intensity at thephotodetector 506-1 can be processed by appropriate sensing logic as achange in state (e.g., a logical “1”) indicative of an object traversingthe detection plane defined by a surface of a generated light curtain502. Likewise, when no part of the object O₁ remains within the lightcurtain, a second state transition occurs when the intensity of theoptical energy received at photodetector 506-1 returns to the earlierstate (e.g., a logical “0”).

FIG. 10B depicts the detection of an object O₂ that includes at leastone light refracting or reflecting portion when object O₂ moves along aconveying path that is traverse a detection plane defined by propagationof collimated optical energy. For example, object O₂ may be an item suchas block contained in a transparent or translucent packaging thatextends beyond the volume of the block. Such an object may have portionsthat are opaque (e.g. the block) and portions that are transparent orreflective (e.g., the packaging that encapsulates the block).

Some of the light emitted by the emitter 506 will pass through clearportions of object O₂ and in configurations in which the emitter isparallel to the surface S, the light may pass through the clear ortranslucent portion so that the system does not detect the object. Inthe present instance, since the light emitted by emitter 506 istransverse the support surface S on which object O₂ is supported, thelight passing through transparent or translucent portions of object O₂may be refracted such that the light does not impinge the detector array508. For example, referring to FIG. 10B, emitted light such as thatpropagating along the ray B_(inc) will strike surfaces of O₂ at anoblique (non-normal) angle. Some of the incident light B_(inc) may bereflected and/or refracted after striking the object O₂. Depending uponthe surface characteristics of object O₂, some or all of the reflectedincident light may be directed away from the photodetectors, as rayB_(ref2), and other portions (e.g. ray B_(ref1)) may be reflected into adifferent photodetector than it would have if all of the light had beentransmitted through the object O₂ (e.g., along ray B_(trans)) or if theobject not been there at all. In this way, the array will detect achange in light from the emitter when the translucent or transparentportions of the object refract light away from the array so that thesystem will detect the object.

As noted previously, the edge detection assembly 500 may be incorporatedinto a vehicle used in the material handling system 10 described above.For instance, turning to FIG. 11 an alternate vehicle 600 isillustrated. The vehicle 600 is substantially similar to the vehicles200 described above, however, the vehicle 600 includes one or more edgedetection assemblies 602, 604 similar to the edge detection assembly 500described above.

Each vehicle 600 may include a single object sensing arrangement forsensing object movement in a single direction along a conveying path.Alternatively, and as shown, each vehicle 600 may include a pair ofobject sensing arrangements in the form of detection assemblies 602 and604. Each vehicle may also include one or more conveyors for conveyingobjects while the objects are on the vehicle. The belt forms a generallyflat or planar surface for supporting objects on the vehicle 600. Forinstance, the conveyor 606 may be a conveyor belt. The first detectionassembly 602 may be positioned adjacent a rear edge of the vehicle 602so that the emitter is positioned below the top surface of the conveyorbelt 606. The detectors of the detection assembly 602 may be positionedabove the surface of the conveyor belt. Additionally, the detectionassembly may be positioned adjacent the rear edge of the conveyor beltso that the surface of the conveyor belt does not extend between theemitter and detector of the detection assembly. In this way, as anobject passes onto the rear edge of the vehicle the object will firstpass between the emitter and detector array of the detection assembly602. Similarly, when an object is being discharged from the rear edge ofthe vehicle, the leading edge of the item will pass between the emitterand detector array of the detection assembly if the leading edge extendspast the end of the conveyor. Similarly, the front detection assembly604 is positioned adjacent the front edge of the vehicle so that frontdetection assembly 604 detects the leading edge of objects as the objectis being loaded onto or discharged from the leading edge of the vehicle.

Detection assembly 602 may, for example, signal a first change in logicstate when an object is moved by conveyor 606 in a first transferdirection “A” such that the leading edge of the object crosses a firstlight curtain detection plane of the edge sensing assembly, aspreviously described in connection with assembly 500. Such a signalwould be indicative of the leading edge of the item being dischargedfrom the rear edge of the vehicle. Likewise, detection assembly 602 maysignal a subsequent (e.g., second) change in logic state if and whencontinued movement of the object by conveyor 606 in the direction Aresults in the trailing edge of the object exiting the first lightcurtain detection plane. Such a signal would be indicative of thetrailing edge of the object being discharged from the rear edge of thevehicle, thereby indicating that the item has been discharged from thevehicle.

Similarly, detection assembly 604 may signal a first change in logicstate when an object is moved by conveyor 606 in a second transferdirection “B” and its leading edge crosses a second light curtaindetection plane of the edge sensing assembly 604. Likewise, detectionassembly 604 may signal a subsequent (e.g., second) change in logicstate if and when continued movement of the object by conveyor 606 inthe direction B results in the trailing edge of the object exiting thesecond light curtain detection plane.

The vehicle 600 may include side walls dimensioned and arranged toprevent translation of an object on conveyor surface 605 as the vehiclemoves along a travel path transverse to the conveyance path directions Aand B. Movement of the conveyor 606 in either the A or B direction is,in some embodiments, performed by a reversible electric motor 610 whichuses a belt 612 to transfer power to conveyor shaft 611. A separatemotor drives the track engaging wheels (e.g., 614 a, 614 b, 614 c) ofvehicle 600 similar to operation of the vehicles 200 describedpreviously.

FIG. 12 is an electrical schematic depicting a circuit 650 comprisingphotodetectors and state sensing logic and operative to signal a changein sensing state when an object traverses the detection plane or lightcurtain along which the phototransistors are arranged, in accordancewith an exemplary embodiment of the present disclosure. In the exemplaryembodiment of FIG. 12, the photodetectors are implemented as NPNphototransistors PT1 to PT10 in respective common emitter amplifiercircuits.

The output of each common-emitter amplifier circuit is created byconnecting a corresponding resistor (R1 to R10) between a voltage supplyVB and the collector pin of the associated phototransistor. The valuesof resistors R1 to R10 are chosen to set the detection threshold (e.g.to discriminate between anticipated levels of ambient light at a giveninstallation). A low value (a few thousand ohms) for the thresholdresistors sets a high threshold level for the incident light to exceedbefore switching takes place (i.e, low sensitivity) while a high valuesets a low threshold level (i.e, high sensitivity). Using, for example,the SFH3710 phototransistor manufactured by Osram Opto SemiconductorsGmbH of Regensburg with a voltage VB on the order of 3.0 to 3.5 volts,under conditions normally applicable to an indoor warehouse environment,a resistance value for R1 to R10 on the order of 300 ohms may yield acircuit which is not impaired by noise or interference from ambientlight sources such as indoor lighting. In addition, or alternatively, afilter which limits the light reaching the phototransistors to arelatively narrow (e.g, +/−2 nm) passband centered at a selectedwavelength within the sensitivity envelope of the phototransistors (notshown) may also be used.

The sensing logic 652 may comprise any arrangement capable of quicklysensing the output of each photodetector and signal and/or process astate change indicative of a light curtain excursion. In one exampleconsistent with the embodiment of FIG. 12, the output of eachphototransistor circuit may be combined using combinatorial logic sothat when the output of any one of the phototransistors falls below thesensitivity threshold, a change in state from “0” to “1” is output bythe sensing logic 652. When the output of all phototransistors returnsto a “0”, a subsequent change in state from “1” to “0” is output bysensing logic 652. In an embodiment, the sensing logic 652 may comprisea field programmable gate array.

In other embodiments, the sensing logic may be implemented by amicroprocessor which senses or samples the output of each respectivephotodetector during a corresponding clock cycle and initiates action inresponse to any of the photodetectors going from a high to a low stateor vice versa and, in a subsequent cycle, when all of the photodetectorsare once again all outputting a high state. In some embodiments, avehicle such as the vehicle 600 of FIG. 11, may include a microprocessorwhich not only monitors the sensing arrangement(s), such as 602 and 604,but also controls the movements of the conveyor 406 and the vehicleitself.

Embodiments consistent with the present disclosure may employ sensingarrangements, such as the arrangement 500 of FIGS. 8-10, in conjunctionwith systems for conveying objects along a conveying path. Such systemsdefine one or more object support surfaces and may further include oneor more object transfer mechanisms respectively operative to move theobject(s) supported by the object support surface in at least one objecttransfer direction. In some embodiments, the support surface(s) may bedefined by surfaces of one or more belt conveyor(s), one or more rollerconveyor(s), one or more tilting table(s), or one or more stationarytables. Where tilting or stationary tables are used, they may haveperforations in fluid communication with a source of pressurized air toreduce friction during an object transfer operation.

Transfer of an object onto or from the object support surface(s) of asystem constructed in accordance with embodiments of the presentdisclosure may be performed in a number of ways. By way of illustrativeexample, a pusher bar or other structure may apply positive forcesmoving the object onto, across, and/or from the object support surface.Alternatively, or in addition, an object supporting surface may itselfbe reoriented (e.g., tilted) by an object transfer mechanism such thatan object moves, by gravity, onto another object support surface or intoa bin or carton at a destination. By way of still further example, anobject transfer mechanism may include a conveyor having, for example, abelt that defines the object support surface. In such embodiments, thebelt may be driven in a first direction to transfer the object toward afirst discharge end of the object transfer mechanism so that it may fallinto, for example, a first waiting container. Similarly, the same beltmay be driven in a second direction to transfer the object toward asecond discharge end of the object transfer mechanism so that it mayfall into, for example, a second waiting container.

In some embodiments, one or more object support surfaces of a materialhandling system and, optionally, one or more object transfer mechanisms,may be moved by a vehicle to an object transfer destination. In oneembodiment, a conveyor equipped vehicle such as vehicle 600 of FIG. 11may be used as part of a material handling system such as an apparatusfor sorting objects into groupings of “n” items, for example. In oneembodiment, “n” is equal to or greater than one and each groupingcomprises the object(s) to be placed in a single shipping carton forshipment to a single customer as part of an order fulfillment process.

In some embodiments an object transfer cycle is initiated when theleading edge of an object enters a detection plane formed by a sensingarrangement such as sensing arrangement 500 of FIGS. 8-10, and an objecttransfer cycle is concluded when the trailing edge of the object exitsthe detection plane/light curtain. Completion of each cycle constitutesconfirmation than the object has been transferred from the objectsupporting surface of vehicle 600 and into one of bins 119. The abilityto accurately detect completion of each cycle for objects of varyingshapes, sizes, and optical properties allows each vehicle to return tothe charging and/or object transfer station 310 without the delays whichmight otherwise be experienced due to a detection failure. As well, therisk of a vehicle leaving a destination proximate one of bins 119 and/orleaving the loading station 130 before a transfer has been fullycompleted is also substantially reduced without regard to the shape andopacity of the objects involved.

Operation

The system 10 operates as follows. An item is processed at the inductionstation 50 to identify a characteristic of the item that is indicativeof where the piece should be sorted. As described previously, the itemmay also be processed to determine whether the item is qualified to betransported by one of the vehicles based on physical characteristics ofthe item. The central controller maintains data that correlates variousdata to identify the destination bin or location for the items beingprocessed.

As discussed previously, the induction station 50 may process the itemsautomatically or manually. In a manual mode, the operator manuallyenters information regarding a piece and then drops the piece on aconveyor. The system electronically tags the piece with the sortinformation and the conveyor conveys the piece toward the loadingstation. Alternatively, if the input system is an automated system, thepiece is automatically scanned to identify the relevant sortcharacteristic. For instance, the input station may use a scanner, suchas a bar code scanner to read the bar code on a piece, or the inputstation may include an imaging device, such as a high speed line scancamera in combination with an OCR engine to read information on thepiece.

To prepare to receive an item, a vehicle 200 moves along the tracktoward the loading station 310 in the loading column 300. When thevehicle 200 moves into position at the loading station 310 the homesensor detects the presence of the vehicle and sends a signal to thecentral processor 350 indicating that the vehicle is positioned at theloading station.

Once the vehicle is positioned at the loading station, the input stationconveys an item onto the vehicle. As the item is being conveyed onto thevehicle 200, the loading mechanism 210 on the vehicle loads the itemonto the vehicle. Specifically, the input station conveys the item intocontact with the conveyor belts 212 on the vehicle. The conveyor belts212 rotate toward the rearward side of the vehicle, thereby driving theitem rearwardly on the vehicle.

The operation of the conveyor belts is controlled by the loading sensors260, 262. The forward loading sensor detects the leading edge of theitem as the item is loaded onto the vehicle. Once the forward loadingsensor 260 detects the trailing edge of the item, a controller onboardthe vehicle determines that the item is loaded on the vehicle and stopsthe conveyor motor. Additionally, the onboard controller may control theoperation of the conveyor in response to signals received from therearward sensor 262. Specifically, if the rearward sensor 262 detectsthe leading edge of the item, then the leading edge of the item isadjacent the rearward edge of the vehicle. To ensure that the item doesnot overhang from the rearward edge of the vehicle, the controller maystop the conveyor once the rearward sensor detects the leading edge ofthe item. However, if the rearward sensor detects the leading edge ofthe item before the forward sensor detects the trailing edge of theitem, the controller may determine that there is a problem with the item(i.e. it is too long or two overlapping items were fed onto the vehicle.In such an instance, the system may tag the piece as a reject anddischarge the item to the reject bin 325 positioned behind the loadingstation. In this way, if there is an error loading an item onto avehicle, the item can simply be ejected into the reject bin, and asubsequent item can be loaded onto the vehicle.

After an item is loaded onto the vehicle, the vehicle moves away fromthe loading station. Specifically, once the onboard controller detectsthat an item is properly loaded onto the vehicle, the onboard controllersends a signal to start the drive motor 250. The drive motor 250 rotatesthe axles, which in turn rotates the gears 222 on the wheels 220. Thegears 222 mesh with the drive surface 156 of the vertical rails 305 inthe loading column to drive the vehicle upwardly. Specifically, thegears and the drive surfaces mesh and operate as a rack and pinionmechanism, translating the rotational motion of the wheels into linearmotion along the track 110.

Since the vehicles move up the loading column from the loading station,the destination for the vehicle does not need to be determined untilafter the vehicle reaches the first gate along the upper rail 135. Forinstance, if an automated system is used at the induction station 50 toscan and determine the characteristic used to sort the items, it maytake some processing time to determine the relevant characteristicand/or communicate that information with a central controller to receivedestination information. The time that it takes to convey the item ontothe vehicle and then convey the vehicle up the loading column willtypically be sufficient time to determine the relevant characteristicfor the item. However, if the characteristic is not determined by thetime the vehicle reaches the upper rail, the system may declare that theitem is not qualified for sorting and the vehicle may be directed to there-induction station 430 to discharge the item onto the dischargeassembly 410. From the re-induction station 430, the vehicle travelsdown the second column to the lower rail 140, and then back to theloading column.

Once the item is qualified for sorting, the central controller 350determines the appropriate bin 190 for the item. Based on the locationof the bin for the item, the route for the vehicle is determined.Specifically, the central controller determines the route for thevehicle and communicates information to the vehicle regarding the bininto which the item is to be delivered. The central controller thencontrols the gates along the track to direct the vehicle to theappropriate column. Once the vehicle reaches the appropriate column thevehicle moves down the column to the appropriate bin. The vehicle stopsat the appropriate bin 190 and the onboard controller sends anappropriate signal to the conveyor motor 255 to drive the conveyor belts212, which drives the item forwardly to discharge the item into the bin.Specifically, the top of the vehicle aligns with the gap between theappropriate bin 190 and the bottom edge of the bin that is immediatelyabove the appropriate bin.

In the present instance, the orientation of the vehicles does notsubstantially change as the vehicles move from travelling horizontally(along the upper or lower rails) to vertically (down one of thecolumns). Specifically, when a vehicle is travelling horizontally, thetwo front geared wheels 220 cooperate with the upper or lower horizontalrail 135 or 140 of the front track 115, and the two rear geared wheels220 cooperate with the corresponding upper or lower rail 135 or 140 ofthe rear track 120. As the vehicle passes through a gate and then into acolumn, the two front geared wheels engage a pair of vertical legs 130in the front track 115, and the two rear geared wheels engage thecorresponding vertical legs in the rear track 120.

As the vehicle travels from the horizontal rails to the vertical columnsor from vertical to horizontal, the tracks allow all four geared wheelsto be positioned at the same height. In this way, as the vehicle travelsalong the track it does not skew or tilt as it changes between movinghorizontally and vertically.

Traffic Control

Since the system includes a number of vehicles 200, the system controlsthe operation of the different vehicles to ensure the vehicles do notcollide into one another. In the following discussion, this is referredto as traffic control. Exemplary methodologies for controlling the flowof traffic are described in U.S. Pat. No. 7,861,844.

In the present instance, some of the columns may have two vertical rails130 that are independent from the adjacent columns. For instance, theloading column 300 has two independent rails that are not shared withthe adjacent column. Therefore, vehicles can travel up the loadingcolumn without regard to the position of vehicles in the column next tothe loading column. Furthermore, as shown in FIG. 5, it may be desirableto configure the column next to the loading column so that it also hastwo independent vertical rails. In this way, vehicles can more freelytravel up the loading column and down the adjacent column.

In the foregoing discussion, the sorting of items was described inrelation to an array of bins disposed on the front of the sortingstation 100. However, as illustrated in FIGS. 3-4, the number of bins inthe system can be doubled by attaching a rear array of bins on the backside of the sorting station. In this way, the vehicles can deliver itemsto bins on the front side of the sorting station by traveling to the binand then rotating the conveyor on the vehicle forwardly to eject thepiece into the front bin. Alternatively, the vehicles can deliver itemsto bins on the rear side of the sorting station by traveling to the binand then rotating the conveyor on the vehicle rearwardly to eject thepiece into the rear bin. Additionally, the sorting station 100 ismodular and can be readily expanded as necessary simply by attaching anadditional section to the left end of the sorting station.

Vehicle Control Based on Item Characteristic(s)

1. Vehicle Movement Profile

As discussed previously, one or more characteristics of an item beingtransported by a vehicle may be detected or determined for the itemduring processing. This detected information can be used to control thefurther processing of the item. In particular, the control of thevehicle between the loading station 310 and the destination bin 190 maybe varied in response to the detected information. More specifically,the movement of the vehicle along the track may be varied in response tothe detected characteristic(s).

A variety of movement variables for the vehicle may be varied based onthe detected information. The list of movement variables includes, butis not limited to: acceleration profile (i.e. how rapidly the vehicleaccelerates), braking profile (i.e. how rapidly the vehicle brakes) andcornering speed (i.e. how fast the vehicle goes around corners). Anothermanner in which the vehicle may be controlled in response to thedetected information is the manner in which items are ejected from thevehicle. In particular, the belt speed of the vehicle may be increasedor decreased to vary the speed with which an item is ejected.

By way of example, the system may have a default control profile that isused to control the movement of the vehicles along the track. Under thedefault profile, the vehicle moves along the track at first peakvelocity, accelerating at a first rate and braking at a first rate.Additionally, under the default movement profile, the vehicle has afirst peak speed as the vehicle travels around a curve from horizontalto vertical or from vertical to horizontal. The default profile mayapply to a variety of items having a series of characteristics that fitwithin a default characteristic profile, such as flat items having areasonable weight (e.g. a book, a box weighing a few ounces or more,etc.). However, if the system detects a characteristic that varies fromthe default characteristic profile, the system may vary the control ofthe vehicle movement. In particular, the system may control the movementaccording to a second movement profile. For example, if the systemdetects that an element is cylindrical the system may control thevehicle according to a movement profile that is different than thedefault profile. The vehicle may accelerate more slowly than the defaultprofile to reduce the likelihood of the item rolling on the vehicle.Similarly, the vehicle may brake more slowly and may travel aroundcorners at a slower rate to reduce the likelihood of the item rolling onthe vehicle.

As discussed above, the control of the vehicle may be controlledaccording to a movement profile and the movement profile may vary basedon one or more characteristics determined for the item to be conveyed bythe vehicle. It should be understood that the system may store a numberof movement profiles, each of which controls the movement of the vehiclealong the track according to different parameters. Each movement profilemay correlate to one or more characteristics of a particular item. Inthis way, a variety of items having one or more shared characteristicmay share the same movement profile. For instance, all fragile non-rounditems may all share the same movement profile and all fragile round orcylindrical items may all share the same movement profile.

In this way, the system can dynamically control the movement of eachvehicle based on one or more characteristic determined for each itembeing carried by each vehicle. The characteristic can be determined byeither directly detecting the characteristic (scanning, weighing,measuring etc.) or the characteristic(s) may be stored in a centraldatabase and the characteristic(s) are determined by identifying theitem, such as by a product code. In addition to or instead of storinginformation about the characteristics for an item, the database maysimply include data that identifies the movement profile to be used foran item. In such an instance, the system or operator scans an item todetect a product identification characteristic (such as a bar code orother identifying information). The vehicle movement profile isidentified in the central base for the item so that the system retrievesthe vehicle movement profile data from the central database after theitem is identified.

2. Vehicle Destination Control

As discussed above, the system can control the movement of the vehiclebased on detected or determined information about the item beingconveyed on the vehicle. Additionally, the destination of the vehiclemay be varied based on one or more characteristic(s) of an item. Forinstance, information regarding the physical characteristics of variousitems may be stored in a central data base. By scanning an item for aproduct identification code the system can retrieve the data regardingthe physical characteristics of the item from the central data base.This data is the expected physical characteristics for the item. Forexample, based on the data stored for a product identification code, theitem may be expected to be 5″ long, 3″ wide and weigh 8 ounces. If thescanning station 80 measures the item to be 8″ long and/or weigh 16ounces, the system may modify the destination for the item.Specifically, based on the scanned product code the system may directthe vehicle to deliver the item to bin “X”. However, when the systemdetects a physical characteristic that does not match the expectedcharacteristic the system may alter the destination bin. In the exampleabove, if the item is scanned and weigh 16 ounces, the system maydeliver the item to bin “y”, which may be an alternate larger bin or maybe an outsort or reject bin for receiving items that vary from theexpected physical characteristic.

3. Vehicle Delivery Control

The system may also control how an item is discharged or delivered at anoutput bin 190 based on the determined or detected physicalcharacteristics of an item. If an item is fragile, the system maycontrol the vehicle so that the conveyor belts rotate more slowly todischarge the item into the output bin more slowly. Additionally oralternatively, the position of the vehicle relative to the output binmay be varied based on the detected or determined characteristic. Forexample, if an item is fragile, the system may stop the vehicle lowerrelative to the bin so that the item is closer to the bottom of the binand therefore has less of a vertical fall when the item is dischargedinto the bin.

Referring now to FIGS. 9 and 10, when multiple items are to be deliveredto the same output bin 190, the system may control the position of thevehicle 200 relative to the output bin 190 to reduce the distance thatthe items must fall when being discharged and to reduce the likelihoodof the items causing a jam as the items stack on top of one another. Thecontrol of the position of the vehicle during delivery may be varieddepending on the detected or determined characteristic(s) of one or moreof the items being sorted to the delivery bin.

As shown in FIGS. 9 and 10 when multiple items are to be delivered to asingle bin, the system may divide the single output bin into threevirtual sort destinations. The system then sorts the three items to thethree virtual sort locations. For instance, as shown in FIG. 9, whenviewed from the front, the output bin 190 may be segmented into threevirtual sort locations: location 1, location 2, and location 3. In FIG.9 the single output bin is divided into three virtual locations havingequal height. However, the size of each virtual location may be variedbased on one or more characteristic determined or detected for an item.Additionally, the virtual locations can be prioritized based on thedetermined or detected characteristic(s) of the items. For instance, ifa plurality of items are to be delivered to an output bin and one of theitems is fragile and one of the items is heavy and/or dense, the systemmay prioritize the virtual locations by prioritizing the heavy item tobe delivered into the bin first and the fragile item is delivered intothe bin second to minimize the likelihood of damage. In order toprioritize the order of delivery, the system may control the flow ofvehicles to stage or delay the vehicle transporting the fragile item.

Similarly, rather than virtually split a single output bin into aplurality of sort locations, the system may virtually merge a pluralityof bins into a single virtual bin based on the characteristicsdetermined or detected for multiple items in an order. For instance, ifmultiple items are to be delivered to a single output bin, but thephysical attributes of the different items dictates the order in whichthe items should be placed into the bin, the system may deliver theitems to two or more bins (preferably adjacent bins). The items are thensorted to the different bins. Returning again to the example of a firstitem that is fragile and a second item that is heavy, when the systemdetects or determines these features, the system may dynamicallyreassign the delivery of the items to two separate output bins ratherthan a single bin if the fragile item is delivered to the output binbefore the vehicle with the second item reaches the output bin. Afterthe two items are delivered to two separate bins, the system provides asignal to the operator indicating that the items in the two separatebins should be withdrawn together and treated as a single order ratherthan being two separate orders.

When an output bin is separated into multiple sort locations as shown inFIG. 9, the system may control the operation of the vehicles to vary theposition of the vehicle relative to the output bin. For instance,referring to FIG. 10, when the vehicle carrying the first item to theoutput bin arrives at the output bin, the system controls the vehicle toadvance the vehicle into alignment with the lowest location for theoutput bin (e.g. Location 1 in FIG. 10) and the item is ejected into thebin so that the first item is on the bottom of the bin. The vehiclecarrying the second item to be delivered to the output bin is thenadvanced so that the vehicle is aligned with the next lowest location ofthe output bin (i.e. Location 2) and the vehicle ejects the item intothe bin so that the second item is placed onto the first item. Finally,the vehicle carrying the third item to be delivered to the output bin isthen advanced so that the vehicle is aligned with the highest locationof the output bin (i.e. Location 3) so that the third item is ejected onthe first and second items.

As shown in FIG. 10, the rear wall of the output bin 190 may be open sothat the vehicles can discharge items through the back of the output binat varying heights along the height of the output bin. However, itshould be appreciated that rather than having an open back wall, theback wall may be displaceable or collapsible to allow the vehicles tostop at varying positions along the height of the output bin anddischarge items into the bin.

As described above, various parameters of how an item is delivered to anoutput bin may be varied based on the physical characteristic(s)determined or detected for an item. Additionally, the system may includeadditional elements that are optionally used during delivery based onthe determined or detected characteristics for the items. For example,the vehicles may include a separate extendable belt or the conveyorbelts 212 may be mounted onto a carriage that can be displaced relativeto the wheels of the vehicle so that the conveyor belts can extend ortelescope outwardly toward the output bin. Specifically, the conveyorbelts may extend into the output bin and the conveyor belts can therotate forwardly to discharge the belt into the output bin. Be extendingthe conveyor belts into the output bin the item drops less when it isdelivered into the output bin. Additionally, the conveyor belt may becontrolled so that the conveyor belt does not start until the conveyorbelt is completely extended into the output bin. The conveyor belt isrotated to discharge the item. While the conveyor belt is rotating, theconveyor belt is retracted toward the vehicle. The simultaneousoperation of discharging the item while withdrawing the belt drops theitem more gently into the output bin.

Alternatively, rather than utilizing an extendable conveyor belt, thesystem may selectively utilize a chute at the output bin in response tothe detection or determination of a physical characteristic of an item.Specifically, in response to detection or determination of an itemhaving a select characteristic, the system may advance the vehicle to aparticular output bin. A chute may be mounted on the rack and thevehicle may drive the chute so that the item is discharged down thechute into the output bin.

It will be recognized by those skilled in the art that changes ormodifications may be made to the above-described embodiments withoutdeparting from the broad inventive concepts of the invention. Forinstance, in the foregoing discussion the system is described as aseries of vehicles guided by a track. However, it should be understoodthat the system need not include a track. For example, the vehicles maytravel along the ground rather than traveling along a track. Thevehicles may be guided along the ground by one or more sensors and/or acontroller. Optionally, the vehicles may be guided in response tosignals from other vehicles and/or from a central controller, such as acomputer that monitors each of the vehicles and controls movement of thevehicles to prevent the vehicles from colliding with one another.Additionally, the central controller may provide signals to direct eachvehicle along a path to a storage location or transfer location.

In addition to a system in which the vehicles move along the groundwithout a track, the system may incorporate a guidance assembly thatincludes one or more rails or other physical guides that contact amechanism on the vehicle to direct the vehicle along a path. Forinstance, the vehicles may each include one or more contact elementssuch as wheels, rollers, guide tabs, pins or other elements that mayengage the guidance assembly. The guidance assembly mail be a linearelement such as a straight rail or it may be a curved element. Theguidance assembly may curve within a horizontal plane so that the railstays within a plane or the guide may curve vertically so that the railis within a single plane. The guidance assembly may include a pluralityof guides or rails vertically spaced from one another so that thevehicles may move horizontally at a plurality of vertical levels. Theguide may also include an elevator for moving the vehicles between thevertically spaced rails.

As can be seen from the above, the system may be incorporated into avariety of systems that use physical guide mechanisms or guide thevehicles along open areas by directing the path to guide the vehicles tostorage locations or transfer locations. As discussed above, themovement of each vehicle may be controlled in response to adetermination of one or more physical characteristics of the itemcarried by each respective vehicle.

The systems and methods described herein may be implemented in software,hardware, or a combination thereof, in different embodiments. Inaddition, the order of methods may be changed, and various elements maybe added, reordered, combined, omitted or otherwise modified. Allexamples described herein are presented in a non-limiting manner.Various modifications and changes may be made as would be obvious to aperson skilled in the art having benefit of this disclosure.Realizations in accordance with embodiments have been described in thecontext of particular embodiments. These embodiments are meant to beillustrative and not limiting. Many variations, modifications,additions, and improvements are possible. Accordingly, plural instancesmay be provided for components described herein as a single instance.Boundaries between various components, operations and data stores aresomewhat arbitrary, and particular operations are illustrated in thecontext of specific illustrative configurations. Other allocations offunctionality are envisioned and may fall within the scope of claimsthat follow. Finally, structures and functionality presented as discretecomponents in the example configurations may be implemented as acombined structure or component. These and other variations,modifications, additions, and improvements may fall within the scope ofembodiments as defined in the claims that follow.

It should therefore be understood that this invention is not limited tothe particular embodiments described herein, but is intended to includeall changes and modifications that are within the scope and spirit ofthe invention as set forth in the claims.

The invention claimed is:
 1. A delivery vehicle cooperable with amaterial handling system for delivering items to a plurality of sortlocations positioned along a track, wherein the delivery vehiclecomprises: a support surface for supporting one of the items to bedelivered; a transfer mechanism configured to load an item onto thesupport surface or to discharge an item from the surface; a plurality ofwheels configured to cooperate with the track to drive the vehiclevertically; a motor operable to drive the plurality of wheels; anedge-detection assembly for detecting an edge of an item when the itemis conveyed onto or discharged from the vehicle, wherein theedge-detection assembly comprises: an emitter for emitting a beam towardthe support surface; and a plurality of detectors for detecting thebeam; wherein one of the emitter and the plurality of detectors isadjacent a discharge end of the support surface and below the dischargeend of the support surface so that the emitter and plurality ofdetectors form a detection plane that is transverse a plane defined bythe support surface; wherein the emitter or the plurality of detectorsare positioned so that an object intersecting the detection planeaffects the beam received by the detectors; and a controller forcontrolling operation of the vehicle, wherein the controller isconfigured to control operation of the transfer mechanism in response tosignals from the edge-detection assembly.
 2. The delivery vehicle ofclaim 1 wherein the emitter and plurality of detectors are positioned sothat the detection plane extends below the support surface.
 3. Thedelivery vehicle of claim 2 wherein the emitter and the plurality ofdetectors are positioned so that the detection plane is at the dischargeend.
 4. The delivery vehicle of claim 3 wherein the emitter and theplurality of detectors are configured so that the detection plane issubstantially normal to the support surface.
 5. The delivery vehicle ofclaim 1 wherein the plurality of detectors comprises a linear array ofaligned detectors.
 6. The delivery vehicle of claim 1 comprising amirror wherein the emitter emits the beam of light toward the mirror andthe mirror reflects the beam toward the plurality of detectors.
 7. Thedelivery vehicle of claim 6 wherein the emitter and the plurality ofdetectors are mounted on a first support element and the mirror ismounted on a second support element spaced apart from the first supportelement.
 8. The delivery vehicle of claim 1 wherein the first supportelement is mounted adjacent a first edge of the surface and the secondsupport element is mounted adjacent a second edge of the surface so thatthe first and second support are on opposite sides of the vehicle. 9.The delivery vehicle of claim 1 wherein the emitter comprises a lens fordispersing the beam to create a beam having sufficient height to impingeon each of the detectors.
 10. The delivery vehicle of claim 1 whereinthe transfer mechanism comprises a conveyor belt or a plurality ofrollers and wherein the conveyor belt or rollers comprises an outersurface forming the support surface.
 11. A delivery vehicle fordelivering items to a plurality of sort locations, wherein the deliveryvehicle comprises: a transfer mechanism configured to load an item ontoa generally horizontal surface or to discharge an item from thehorizontal surface; a plurality of wheels configured to cooperate with atrack to drive the vehicle vertically; a motor operable to drive theplurality of wheels; a sensing assembly for sensing an item when theitem is conveyed onto or discharged from the vehicle, wherein thesensing assembly comprises: an emitter for emitting a beam toward thesurface, wherein the emitter is positioned below the surface so that thebeam is projected transverse the horizontal surface; and a plurality ofdetectors for detecting the beam; wherein one of the emitter and theplurality of detectors is adjacent a discharge end of the surface andbelow the discharge end of the surface and wherein the emitter andplurality of detectors cooperate to form a detection plane that istransverse a plane defined by the horizontal surface; wherein theemitter or the plurality of detectors are positioned so that an objectintersecting the detection plane affects the beam received by thedetectors; and a controller for controlling operation of the vehicle,wherein the controller is configured to control operation of thetransfer mechanism in response to signals from the sensing assembly. 12.The delivery vehicle of claim 11 wherein the plurality of wheelscomprise a first set of wheels configured to cooperate with a firsttrack and a second set of wheels configured to cooperate with a secondtrack so that the delivery vehicle is moveable within an aisle betweenthe first track and the second track.
 13. The delivery vehicle of claim11 wherein the transfer mechanism comprises a conveyor belt or aplurality of rollers and wherein the conveyor belt or rollers comprisesan outer surface forming the horizontal surface.
 14. The deliveryvehicle of claim 11 wherein the plurality of detectors comprise aplurality of photodetector elements disposed in a linear array.
 15. Thedelivery vehicle of claim 14 comprising a lens system dimensioned andarranged to receive optical energy from the emitter and to collimate thereceived optical energy into a line aligned with the plurality ofphotodetector elements, wherein optical energy of the line is receivedby each photodetector element of the plurality of photodetector elementsunless an amount of optical energy above a sensitivity threshold isabsorbed, reflected or refracted by an object intersecting the detectionplane.
 16. The delivery vehicle of claim 11 wherein the emitter andplurality of detectors are positioned so that the detection planeextends below the support surface.
 17. The delivery vehicle of claim 11wherein the emitter and the plurality of detectors are configured sothat the detection plane is substantially normal to the support surface.18. The delivery vehicle of claim 17 wherein the plurality of detectorscomprises a linear array of aligned detectors.
 19. A vehicle forconveying objects along a conveying path in a material handling system,comprising: a pair of shafts comprising a first shaft and a second shaftextending in a direction transverse to an object transfer direction; aconveyor belt supported by the pair of shafts, the conveyor beltdefining an object support surface; an electric motor for driving atleast one of the shafts and causing movement of the conveyor belt andany object disposed on the object support surface following movement ofthe vehicle along the conveying path to an object transfer location; anda sensing arrangement for sensing an intersection between an object anda detection plane transverse to a plane defined by the object supportsurface, the sensing arrangement including: a plurality of photodetectorelements disposed in a linear array; a light source; and a lens systemdimensioned and arranged to receive optical energy from the light sourceand to collimate the received optical energy into a line aligned withthe plurality of photodetector elements, wherein optical energy of theline is received by each photodetector element of the plurality ofphotodetector elements unless an amount of optical energy above asensitivity threshold is absorbed, reflected or refracted by an objectdisposed on the object support surface; wherein the electric motor iscontrolled in response to signals received from the sensing arrangement.20. The delivery vehicle of claim 19 wherein the emitter and pluralityof detectors are positioned so that the detection plane extends belowthe support surface.
 21. The delivery vehicle of claim 19 wherein theemitter and the plurality of detectors are configured so that thedetection plane is substantially normal to the support surface.
 22. Thedelivery vehicle of claim 21 wherein the plurality of detectorscomprises a linear array of aligned detectors.